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N_Queen.cpp
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N_Queen.cpp
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#include <bits/stdc++.h>
#include <iostream>
using namespace std;
class Solution {
public:
void solve(int col, vector < string > & board, vector < vector < string >> & ans, vector < int > & leftrow, vector < int > & upperDiagonal, vector < int > & lowerDiagonal, int n) {
if (col == n) {
ans.push_back(board);
return;
}
for (int row = 0; row < n; row++) {
if (leftrow[row] == 0 && lowerDiagonal[row + col] == 0 && upperDiagonal[n - 1 + col - row] == 0) {
board[row][col] = 'Q';
leftrow[row] = 1;
lowerDiagonal[row + col] = 1;
upperDiagonal[n - 1 + col - row] = 1;
solve(col + 1, board, ans, leftrow, upperDiagonal, lowerDiagonal, n);
board[row][col] = '.';
leftrow[row] = 0;
lowerDiagonal[row + col] = 0;
upperDiagonal[n - 1 + col - row] = 0;
}
}
}
public:
vector < vector < string >> solveNQueens(int n) {
vector < vector < string >> ans;
vector < string > board(n);
string s(n, '.');
for (int i = 0; i < n; i++) {
board[i] = s;
}
vector < int > leftrow(n, 0), upperDiagonal(2 * n - 1, 0), lowerDiagonal(2 * n - 1, 0);
solve(0, board, ans, leftrow, upperDiagonal, lowerDiagonal, n);
return ans;
}
};
int main() {
int n = 4; // we are taking 4*4 grid and 4 queens
Solution obj;
vector < vector < string >> ans = obj.solveNQueens(n);
for (int i = 0; i < ans.size(); i++) {
cout << "Arrangement " << i + 1 << "\n";
for (int j = 0; j < ans[0].size(); j++) {
cout << ans[i][j];
cout << endl;
}
cout << endl;
}
return 0;
}